1. Field of the Invention
The present application relates to the field of electronics, and more particularly, to methods of forming interconnection bumps and related structures.
2. Description of the Related Art
C4 (Controlled-Collapse Chip Connection) is used to connect IC (integrated circuit) chips to substrates in electronic packages. Moreover, C4 is a flip-chip technology in which the interconnections may be provided using relatively small solder balls on the chip surface. Because it is an area array, C4 technology may provide relatively high densities for chip interconnections.
C4 technology has been used since the 1960s and has proven reliable in the semiconductor field. Historically, PbSn (lead-tin) solder has been evaporated through a metal mask.
Recently, due to environmental and other concerns, the use of lead containing solder has been discouraged, restricted or otherwise prohibited. Instead of using lead, solder bumps are formed by electroplating a metal alloy material. Unfortunately, electroplating metal alloy solder bumps is very difficult, requiring careful monitoring and control of the electroplating bath chemistry. Accordingly, the cost of electroplating metal alloy solder is relatively high and the associated yield is relatively low.